diff --git a/test/hooked_test.dart b/test/hooked_test.dart
index b4856dc9..509dcd41 100644
--- a/test/hooked_test.dart
+++ b/test/hooked_test.dart
@@ -6,7 +6,7 @@ import 'package:test/test.dart';
 import 'common.dart';
 
 main() {
-  Map headers = {
+  Map headers = <String, String>{
     'Accept': 'application/json',
     'Content-Type': 'application/json'
   };
diff --git a/test/routing_test.dart b/test/routing_test.dart
index 5e53c496..184970b6 100644
--- a/test/routing_test.dart
+++ b/test/routing_test.dart
@@ -154,7 +154,7 @@ main() {
   });
 
   test('Can serialize function result as JSON', () async {
-    Map headers = {'Content-Type': 'application/json'};
+    Map headers = <String, String>{'Content-Type': 'application/json'};
     String postData = json.encode({'it': 'works'});
     var response = await client.post("$url/lambda",
         headers: headers as Map<String, String>, body: postData);